Torque-indication crush washer

ABSTRACT

An apparatus comprises a metal washer having an outer circumference, a plurality of cavities formed within the washer, wherein each cavity has an opening that is flush with the outer circumference, an indicator material comprising an inspection lacquer within at least one of the cavities, and a membrane along the outer circumference sealing the inspection lacquer within the cavity.

This application is a continuation of U.S. patent application Ser. No.13/487,810, filed Jun. 4, 2012. The content of the above application ishereby incorporated by reference.

BACKGROUND

Crush washers are used to seal fluid or gas connections such as thosefound in an internal combustion engine. For instance, crush washers areused to provide a seal between an oil pan and a drain bolt to preventengine oil from leaking. Similarly, crush washers are used to seal theconnection between a transfer case pan and a drain bolt to prevent gearoil from leaking and between a transmission pan and a drain bolt toprevent transmission fluid from leaking. There are many otherapplications within an internal combustion engine where a crush washermay be utilized.

When the drain bolt is tightened onto the pan, care must be taken toavoid over-torqueing of the bolt as this may cause the pan to becomecracked. The crush washer provides a margin of safety in that the crushwasher is designed to deform when a torque sufficient to prevent leakinghas been applied to the bolt. The deforming of the crush washer allowsthe bolt to be over-torqued a slight amount before damage to the panoccurs. There are instances, however, when the deformation of the crushwasher may go unnoticed. In such instances, if torque continues to beapplied to the bolt, then this margin of safety is overcome and the panmay become damaged and/or leak.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a torque-indicating crush washer formedin accordance with an implementation of the invention showing onecavity.

FIG. 2 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showingfour relatively narrow cavities.

FIG. 3 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showingfour relatively wide cavities.

FIG. 4 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showing onecavity that extends around the entire circumference of the crush washer.

FIG. 5 is a top view and a side view of the torque-indicating crushwasher of FIG. 4, but filled with an indicator material that is sealedwithin the crush washer by an outer membrane.

FIG. 6 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showingeight relatively narrow and deep cavities.

FIG. 7 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showingeight relatively narrow and shallow cavities.

FIG. 8 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showingfour relatively wide cavities that extend through the center of thecrush washer.

FIG. 9 is a top view and a side view of a torque-indicating crush washerformed in accordance with an implementation of the invention showingfour relatively narrow cavities that are formed directly within thecrush washer without the use of an outer membrane.

FIG. 10 is a top view and a side view of a torque-indicating crushwasher formed in accordance with an implementation of the inventionshowing six relatively narrow and unevenly distributed cavities.

FIG. 11 is a top view and a side view of a torque-indicating crushwasher formed in accordance with an implementation of the inventionshowing a relatively wider center portion.

FIG. 12 is a top view and a side view of a torque-indicating crushwasher formed in accordance with another implementation of the inventionhaving curved top and bottom surfaces.

FIG. 13 is a top view and a side view of a torque-indicating crushwasher formed in accordance with yet another implementation of theinvention having crush bumps formed over the cavities.

DETAILED DESCRIPTION

Described herein is a crush washer that provides a visual indication ofwhen a sufficient amount of torque has been applied to a bolt. In thefollowing description, various aspects of the illustrativeimplementations will be described using terms commonly employed by thoseskilled in the art to convey the substance of their work to othersskilled in the art. However, it will be apparent to those skilled in theart that the present invention may be practiced with only some of thedescribed aspects. For purposes of explanation, specific numbers,materials and configurations are set forth in order to provide athorough understanding of the illustrative implementations. However, itwill be apparent to one skilled in the art that the present inventionmay be practiced without the specific details. In other instances,well-known features are omitted or simplified in order not to obscurethe illustrative implementations.

FIG. 1 is a perspective view of a torque-indicating crush washer 100constructed in accordance with a first implementation of the invention.Similar to a conventional washer, the torque-indicating crush washer 100consists of an annulus having an inner diameter D₁ and an outer diameterD₀. The torque-indicating crush washer 100 includes a center hole 102through which a bolt, a screw, or another similar item may be insertedor threaded.

The range of lengths for inner diameter D₁ and an outer diameter D₀ cancover over any conceivable lengths imaginable for a washer. For example,in some implementations of the invention, the inner diameter D₁ canrange from one millimeter (1 mm) to 200 mm and the outer diameter D₀ canrange from just over 1 mm to over 200 mm. Nanotechnology applicationsfor the torque-indicating crush washer 100 of the invention may uselengths of less than 1 mm for both the inner diameter D₁ and an outerdiameter D₀. Similarly, large-scale applications for thetorque-indicating crush washer 100 may use lengths greater than 200 mmfor the inner diameter D₁ and an outer diameter D₀.

The torque-indicating crush washer 100 also has a thickness T. In someimplementations of the invention, the thickness T of thetorque-indicating crush washer 100 can range from less than 1 mm toaround 50 mm. Nanotechnology applications for the torque-indicatingcrush washer 100 of the invention may use a thickness T that is lessthan 1 mm. Similarly, large-scale applications for the torque-indicatingcrush washer 100 may use a thickness T that is greater than 200 mm.

It should be noted that the dimensions of the torque-indicating crushwasher 100 will vary based upon its intended application. For instance,the dimensions of a torque-indicating crush washer 100 that is used foran automotive application may differ from the dimensions of atorque-indicating crush washer 100 that is used for a motorcycleapplication or a boat application. The specific dimensions providedherein are not intended to restrict or otherwise limit the scope andspirit of the invention.

In accordance with implementations of the invention, thetorque-indicating crush washer 100 includes one or more cavities 104formed along its perimeter. Each cavity 104 consists of an open hollowor void with an opening that is flush with an outer perimeter orcircumference of the torque-indicating crush washer 100. The number ofcavities 104 will vary in different implementations of the invention.For instance, in the implementation shown in FIG. 1, thetorque-indicating crush washer 100 includes a single cavity 104. In theimplementations shown in FIGS. 2 and 3, the torque-indicating crushwasher 100 includes four cavities 104. And the implementations shown inFIGS. 6 and 7 illustrate a torque-indicating crush washer 100 havingeight cavities 104. There is no limit to the number of cavities 104 thatmay be formed in the torque-indicating crush washer 100. In accordancewith the various implementations of the invention, the number ofcavities 104 formed is based on factors such as the intended use of thetorque-indicating crush washer 100, the amount of torque or force thatthe torque-indicating crush washer 100 is designed to withstand, thetechnology and materials used to build the torque-indicating crushwasher 100, as well as the specific dimensions of the torque-indicatingcrush washer 100 itself. For example, the use of nanotechnologyprocesses and materials may enable the formation of millions of cavities104 in the torque-indicating crush washer 100. And as another example, atorque-indicating crush washer 100 that is designed to tolerate arelatively high degree of force or torque may include fewer cavities 104to improve its mechanical integrity.

Each cavity 104 has a cavity width C_(W), which is measured across theopening of the cavity 104 and along the perimeter of thetorque-indicating crush washer 100. Each cavity 104 also has a cavityheight C_(H) measured across the opening of the cavity 104 but along thethickness of the torque-indicating crush washer 100. Finally, eachcavity 104 has a cavity depth C_(D) that provides a distance from theopening of the cavity 104 to the bottom of the cavity 104. The bottom ofthe cavity 104 may be located proximate to the center hole 102 of thetorque-indicating crush washer 100 in some implementations.

In implementations of the invention, the depth C_(D) of the cavity 104will be a value that is less than one-half the difference between theouter diameter D₀ and the inner diameter D₁. In other words:C _(D)<(D ₀ −D ₁)/2

In an alternate implementation described below in FIG. 8, the cavitydepth C_(D) may be equal to one-half the difference between the outerdiameter D₀ and the inner diameter D₁. In other words:C _(D)=(D ₀ −D ₁)/2

In one implementation of the invention, shown in FIGS. 4 and 5, thecavity width C_(W) is equal to the circumference of thetorque-indicating crush washer 100. In this implementation there are noindividual cavities 104, instead, the entire interior of thetorque-indicating crush washer 100 is hollow.

The cavities 104 may be regularly or irregularly spaced around thecircumference of the torque-indicating crush washer 100. In one specificimplementation, the torque-indicating crush washer 100 may include fourevenly spaced cavities 104, as shown in FIGS. 2 and 3. In anotherspecific implementation, the torque-indicating crush washer 100 mayinclude eight evenly spaced cavities 104, as shown in FIGS. 6 and 7. Andas shown in FIG. 10, the cavities 104 may be distributed around thetorque-indicating crush washer 100 in an irregular pattern. FIG. 10illustrates six cavities 104 arranged in an irregular pattern, but infurther implementations, more or less than six cavities 104 may bearranged in an irregular pattern.

The torque-indicating crush washer 100 may be formed using a malleablemetal or any other material suitable for use in a conventional crushwasher. In some implementations of the invention, the torque-indicatingcrush washer 100 may be formed from metals that include, but are notlimited to, copper, copper alloy, aluminum, aluminum alloy, silver,silver alloy, tin, tin alloy, nickel, nickel alloy, as well as alloys ofthese or other metals used in similar applications. In furtherimplementations, one or more of the following metals may be used to formthe torque-indicating crush washer 100: zinc, molybdenum, carbon,manganese, cadmium, titanium, chromium, iron, cobalt, zirconium,niobium, technetium, ruthenium, rhodium, palladium, hafnium, tantalum,tungsten, rhenium, osmium, iridium, platinum, gold, mercury,rutherfordium, dubnium, seaborgium, bohrium, hassium, copernicium,gallium, indium, thallium, lead, vanadium, and bismuth.

In alternate implementations of the invention, a polymer or plasticbased material may be used to form the torque-indicating crush washer100. It should be noted that the material used to form thetorque-indicating crush washer 100 is not limited to a metal, a polymer,or a plastic. Furthermore, the force-tolerance and torque-tolerance ofthe torque-indicating crush washer 100 may be configured for a widevariety of applications by varying the type of material used and/or byvarying the density of the material used. If metal is used, then varyingthe type of metal or metal-alloy used may also configure theforce-tolerance and torque-tolerance of the torque-indicating crushwasher 100.

FIGS. 2 and 3 illustrate top and side views of torque-indicating crushwashers 100 formed in accordance with further implementations of theinvention. Both implementations shown have four regularly spacedcavities 104 formed in the torque-indicating crush washer 100. FIG. 2illustrates cavities 104 that are narrower than the implementation shownin FIG. 3.

Separating walls 106 isolate the cavities 104 of the torque-indicatingcrush washer 100 from one another. The separating walls 106 also provideresistance to the force or torque that is applied when thetorque-indicating crush washer 100 is in use. Therefore, another meansby which the force-tolerance and torque-tolerance of thetorque-indicating crush washer 100 may be configured is by adjusting thewidth or thickness of the separating walls 106.

For example, for high-torque applications where the torque-indicatingcrush washer 100 is configured to become deformed at a relatively highdegree of force and torque, the separating walls 106 may be relativelywide. The relatively wide separating walls 106 provide greater metalvolume within the torque-indicating crush washer 100 and thereby providegreater resistance to the applied force or torque. As shown in FIG. 2,the cavities 104 may be relatively narrow and the separating walls 106are correspondingly wide. As such, the torque-indicating crush washer100 of FIG. 2 may be used in a relatively high-torque application.

For low-torque applications where the torque-indicating crush washer 100is configured to become deformed at a relatively low degree of force andtorque, the separating walls 106 may be relatively narrow. Therelatively narrow separating walls 106 provide less metal volume withinthe torque-indicating crush washer 100 and thereby provide lessresistance to the applied force or torque. As shown in FIG. 3, thecavities 104 may be relatively wide and the separating walls 106 arecorrespondingly narrow. The torque-indicating crush washer 100 of FIG. 3may therefore be used in a relatively low-torque application.

As shown in FIGS. 2 and 3, at least one of the cavities 104 contains anindicator material 202. In accordance with implementations of theinvention, the torque-indicating crush washer 100 is designed such thatwhen a predetermined amount of force or torque is applied, thetorque-indicating crush washer 100 deforms and the indicator material202 discharges from the cavity 104. The discharge of the indicatormaterial 202 from the cavity 104 provides a visual indication that thepredetermined amount of force or torque has been applied to thetorque-indicating crush washer 100.

In some implementations of the invention, when the indicator material202 is discharged from the cavity 104, it will generally adhere tosurfaces proximate to the torque-indicating crush washer 100. Forinstance, if the torque-indicating crush washer 100 is being used in anoil-changing automotive application to seal a connection between a drainbolt and an oil pan, the indicator material 202 may discharge onto thesurface of the oil pan, onto the exterior surfaces of thetorque-indicating crush washer 100, and/or onto the drain bolt itself.In other applications, the indicator material 202 will similarly adhereto surfaces proximate to the torque-indicating crush washer 100,including but not limited to the hand of a user or the tool being usedto apply the torque.

In accordance with one implementation of the invention, the indicatormaterial 202 may be a color such as red, blue, green, yellow, pink, orany other color that enables a user to easily see when the indicatormaterial 202 has been discharged. In accordance with furtherimplementations of the invention, the indicator material 202 may bechosen from a group of materials that includes, but is not limited to, agrease, an oil, an ink, an epoxy, a sealant, a liquid rubber, a glue, acaulking material, a latex, an acrylic, a silicone, a gel, or aninspection lacquer such as Torque-Seal® by Organic Products Co. ofDallas, Tex. In implementations of the invention, the indicator material202 may be a material that is resistant to removal from any surfaces ithas adhered to upon discharging from the torque-indicating crush washer100. In further implementations, the indicator material 202 may consistof a material that is heat-resistant or can tolerate a high heat. In yetfurther implementation of the invention, the indicator material 202 mayconsist of a material that changes composition or physical propertieswhen exposed to air upon discharge, such as a material that hardens orcures when exposed to air.

In some implementations of the invention, the indicator material 202 mayconsist of a material that has the ability to remain on surfacesproximate to the torque-indicating crush washer 100 for long periods oftime. This provides a long-lasting, visual indication that theappropriate amount of torque had been applied. Thus, in situations wheresome time has passed and a question arises concerning whether anappropriate amount of torque had been applied, the presence of theindicator material 202 can confirm that indeed it had.

The top view of FIGS. 2 and 3 further illustrate a membrane 200 that isformed along the outer perimeter of the torque-indicating crush washer100. The membrane 200 seals the cavities 104 to hold the indicatormaterial 202 within the cavity 104 until the indicator material 202 isdischarged through the application of a sufficient force and/or torqueon the torque-indicating crush washer 100. The membrane 200 alsoprevents the indicator material from drying out or curing. Inimplementations of the invention, the membrane 200 may be formed ofmaterials that include, but are not limited to, rubber, plastic,polymer, or metal. In some implementations, the membrane 200 may beformed using the same material that is used to form thetorque-indicating crush washer 100. The force-tolerance andtorque-tolerance of the torque-indicating crush washer 100 may beconfigured for a wide variety of applications by varying the type ofmaterial used to form the membrane 200, by varying the density of thematerial used to form the membrane 200, and/or by varying the thicknessof the membrane 200. It should be noted that to expose the cavities 104,the side view of the torque-indicating crush washer 100 shown in FIGS. 2and 3 does not include the membrane 200.

FIGS. 4 and 5 illustrate an implementation of the invention wherein thecavity 104 extends the entire circumference of the torque-indicatingcrush washer 100. FIG. 4 illustrates the torque-indicating crush washer100 with no membrane 200 and no indicator material 202. As shown in theside view of FIG. 4, the torque-indicating crush washer 100 consists ofa center annulus portion with top and bottom sides that extend out fromthe center portion, similar to a spool. In FIG. 5, the top view showsthe indicator material 202 filling the cavity 104 and a membrane 200that encircles the torque-indicating crush washer 100 and seals theindicator material 202 within the washer 100. The side view of FIG. 5does not illustrate the membrane 200 in order to expose the indicatormaterial 202.

FIGS. 6 and 7 illustrate top and side views of another implementation ofa torque-indicating crush washer 100 that includes eight cavities 104.FIG. 6 illustrates one implementation where the cavities 104 arerelatively deep and extend almost to the center portion of thetorque-indicating crush washer 100. Only a subset of the cavities 104 ofthe torque-indicating crush washer 100 of FIG. 6 are filled withindicator material 202. As mentioned above, not all of the cavities 104are required to be filled with indicator material 202. In someimplementations, empty cavities 104 may be included simply to helpconfigure the force/torque resistance of the torque-indicating crushwasher 100.

FIG. 7 illustrates another implementation where the cavities 104 arerelatively shallow and only extend about a quarter of the way to thecenter portion of the torque-indicating crush washer 100. Here, all ofthe cavities 104 are filled with indicator material 202. In both topviews of FIGS. 6 and 7, a membrane 200 is shown that seals the cavities104. The membrane 200 is not shown in the side views of FIGS. 6 and 7 inorder to expose the cavities 104.

It should be noted that the use of shallow cavities 104 in theimplementation of FIG. 7 results in more metal being included in theinterior region of the torque-indicating crush washer 100 relative tothe implementation of FIG. 6. This causes the implementation shown inFIG. 7 to have increased resistance to any force and/or torque that isapplied. Thus, the force-tolerance and torque-tolerance of thetorque-indicating crush washer 100 may also be configured for a widevariety of applications by varying the depth of the cavities 104.

FIG. 8 illustrates a top view and a side view of a torque-indicatingcrush washer 100 wherein the cavities 104 extend from the outerperimeter all the way through the center hole 102. In thisimplementation two membranes, membrane 200 as well as a second membrane800 used within the center hole 102, are used to seal the cavities 104.In the side view of FIG. 8, the membrane 200 is not shown to expose thecavities 104.

FIG. 9 illustrates a top view and a side view of a torque-indicatingcrush washer 100 wherein the cavities 104 are simply hollows that arefully encapsulated within the body of the crush washer 100 and themembrane 200 is therefore not needed. Since the cavities 104 do notextend to the outer perimeter of the torque-indicating crush washer,this implementation includes ports 900 that are connected to each cavity104 and may be used to inject the indicator material 202 into eachcavity 104. The ports 900 may then be sealed using a metal or anothermaterial to complete formation of the torque-indicating crush washer100. The side view of FIG. 9 does not illustrate the cavities 104.

FIG. 10 illustrates a torque-indicating crush washer 100 wherein thecavities 104 are irregularly spaced. As shown, three cavities 104 areformed towards one side of the torque-indicating crush washer 100 andthree more cavities 104 are formed on the opposite side. Largeseparating walls 106 are formed between the two sets of cavities 104.The membrane 200 is not shown in the side view of FIG. 10 in order toexpose the cavities 104.

FIG. 11 illustrates an implementation of a torque-indicating crushwasher 100 wherein the center portion 102 of the washer 100 is widerthan the edges 1100 of the washer 100. This is more clearly seen in theside view of FIG. 11. When a sufficient force and/or torque is applied,the use of a thicker center portion 102 may direct the indicatormaterial 202 towards the edges 1100 of the torque-indicating crushwasher 100 where it is discharged. The membrane 200 is not shown in theside view of FIG. 11 in order to expose the cavity 104.

FIG. 12 illustrates another implementation of the crush-indicatingwasher 100 wherein the top and bottom surfaces are curved, as shown inthe side view of FIG. 12. When a sufficient force and/or torque isapplied, the use of a curved surface may direct the indicator material202 towards the edges 1100 of the torque-indicating crush washer 100where it is discharged. The membrane 200 is not shown in the side viewof FIG. 12 in order to expose the cavities 104.

FIG. 13 illustrates another implementation of the invention whereincrush bumps 1300 are formed atop one or more of the cavities 104. When aforce and/or torque is applied to the torque-indicating crush washer100, the crush bumps 1300 are generally the first structures to deform.When they deform, the crush bumps 1300 may force the indicator material202 towards the edges 1100 of the torque-indicating crush washer 100where it is discharged. The membrane 200 is not shown in the side viewof FIG. 13 in order to expose the cavity 104.

In some implementations of the invention, the torque-indicating crushwasher 100 may be formed using a molding process, an injection-moldingprocess, a casting process, or a machining process. Most metal makingprocesses that are suitable for making conventional washers may be usedto make the torque-indicating crush washers 100 of the invention. Insome implementations, the torque-indicating crush washer 100 may beformed in two halves that are then joined together.

As mentioned above, the amount of force or torque that is necessary todeform the torque-indicating crush washer 100 will vary based on itsintended use. To this end, the torque-indicating crush washer 100 may bemodified to work over a wide range of forces or torques through theappropriate selection of materials, separating wall dimensions, cavitydimensions, cavity number and placement, and membrane material andthickness.

The above description of illustrated implementations of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific implementations of, and examples for, the invention aredescribed herein for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseskilled in the relevant art will recognize.

These modifications may be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific implementationsdisclosed in the specification and the claims. Rather, the scope of theinvention is to be determined entirely by the following claims, whichare to be construed in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. An apparatus comprising: a washer having a topand bottom surface and an outer circumference; a cavity formed in thewasher; and an indicator material within the cavity; wherein theindicator material is adhesive; wherein the cavity is not coterminouswith (a) an aperture that is centrally located within the washer andwhich connects the top and bottom surfaces to each other; (b) the outercircumference; (c) the top surface; and (d) the bottom surface.
 2. Theapparatus of claim 1 comprising: an additional cavity that does notinclude the indicator material; and wherein (a) the aperture does notdirectly connect to the additional cavity, and (b) the cavity does notdirectly connect to the additional cavity.
 3. The apparatus of claim 1wherein: the aperture includes an inner diameter (D₁); the cavityincludes a cavity depth (C_(D)) that extends from an innermost portionof the cavity radially outwards to an outermost portion of the cavity;the cavity includes a height, taken orthogonal to the depth, whichextends from a top portion of the cavity to bottom portion of thecavity; the washer includes an outer diameter (D₀); and the depth is notgreater than (D₀−D₁)/2.
 4. The apparatus of claim 3, wherein the cavityis closer to the outer circumference than the aperture.
 5. An apparatuscomprising: a washer having a top and bottom surface and an outercircumference; a cavity formed in the washer; an indicator materialwithin the cavity; an aperture that is centrally located within thewasher and connects the top and bottom surfaces to each other; and atorus-shaped membrane containing the indicator material within thecavity; wherein: (a) the cavity circumnavigates the aperture; (b) aportion of the indicator material is equidistant between the top andbottom surfaces; (c) the torus-shaped membrane has a maximum diameterthat is less than both a maximum diameter of the upper surface and amaximum diameter of the lower surface; and (d) the indicator material isadhesive.
 6. The apparatus of claim 5 wherein the indicator material isheat resistant.
 7. The apparatus of claim 5 wherein: the cavity iscoterminous with the aperture.
 8. The apparatus of claim 7 wherein thecavity is fluidly coupled to the aperture.
 9. The apparatus of claim 5wherein the cavity is coterminous with the outer circumference.
 10. Anapparatus comprising: a washer having a top and bottom surface and anouter circumference; a first cavity and a second cavity both formed inthe washer; an aperture, centrally located within the washer, whichconnects the top and bottom surfaces to each other; an indicatormaterial; and a membrane containing the indicator material within thefirst cavity; wherein (a) the first cavity includes a first openinglocated along the outer circumference of the washer and the secondcavity includes a second opening located along the outer circumference,(b) the aperture does not directly connect to either of the first andsecond cavities, (c) the first cavity does not directly connect to thesecond cavity, (d) the membrane seals both of the first and secondopenings.
 11. The apparatus of claim 10 wherein: the indicator materialcures in response to exposure to atmosphere conditions; the membrane isconfigured to prevent the indicator material from curing until themembrane fails in response to force transmitted upon the washer.
 12. Theapparatus of claim 10, wherein: the washer comprises a material selectedfrom the group consisting of a metal, a rubber, or a polymer; and themembrane includes the material.
 13. The apparatus of claim 12, wherein acenter portion of the washer is thicker than an edge portion of thewasher.
 14. The apparatus of claim 10, wherein the indicator materialcomprises a member selected from the group consisting of an epoxy, asealant, a liquid rubber, a glue, a latex, an acrylic, and an inspectionlacquer.
 15. The apparatus of claim 10, wherein the membranecircumnavigates the washer.
 16. The apparatus of claim 10 wherein atleast one of the first and second cavities is coterminous with theaperture at a third opening.
 17. The apparatus of claim 16 comprising asecond membrane that covers the third opening.
 18. The apparatus ofclaim 10 comprising a plurality of cavities in addition to the first andsecond cavities, wherein the first, second, and plurality of cavitiesare not regularly spaced around the aperture with regard to one another.19. An apparatus comprising: a washer having a top and bottom surfaceand an outer circumference; a cavity formed in the washer; an indicatormaterial within the cavity; an additional cavity that does not includethe indicator material; and an aperture centrally located within thewasher that connects the top and bottom surfaces to each other; wherein(a) the aperture does not directly connect to either of the cavity andthe additional cavity, (b) the cavity does not directly connect to theadditional cavity, and (c) the indicator material is adhesive.
 20. Theapparatus of claim 19 wherein the cavity is coterminous with the outercircumference.